DESCRIPTION: (Applicant's Description) During the past funding period, a centralized Protein Purification and Expression core Facility (the PPE Core) has been a essential component of the Program. Operating under the day-to-day supervision of Dr. Dr. Hui Sun, the PPE Core Director, this core facility provided expertise and state-of-the-art equipment and material for protein purification and expression. The PPE core also maintains a central source of expression vectors and cell lines. The PPE Core has now been expanded to support three particular facets of research essential to the projects within this Program: 1. The PPE Core will continue to maintain state-of-the-art facilities for protein purification and expression; and to provide expertise in strategies and techniques of protein purification. It will also continue to maintain a collection of expression vectors, bacterial and yeast strains, resins for chromatography, and media for cell growth. 2. The PPE Core will provide a centralized point for submission of reactions for automated DNA sequence analysis by the W.H. Keck Center for Biotechnology Resources, Yale Medical School. 3. The PPE Core will support screens of high density matrix arrays for cell type-specific gene expression, providing shared access to this rapidly evolving technology.